Spending money is a sign of success - losing money spells failure.
And Musk FAILED in Wisconsin!

He is addicted to money and his self worth is tied up being the richest man in the world. Tesla is losing money which brought tears to his eyes.
So the loss of money will hurt.

He thinks he is the most powerful man in the world.
So yes the loss from that perspective is painful.
He is not the most powerful man in the world and cannot get
everyting he wants.

It's the fact that he couldn't get his way that's probably most galling.

He cares about power. This grates him because his money wasn't able to buy him more power. But this was a trial run, he's going to be trying to buy races in the future. He wants total power.

It's illegal to give a bottle of water to a voter standing in the heat in a half-mile line to vote in Georgia, but you can PAY MONEY to voters in Wisconsin?

would buy rounds of drinks for votes.